This invention relates to a method for manufacturing smart cards in the UICC (Universal Integrated Circuit Card) 2FF, 3FF or 4FF formats. The smart cards may for example be SIM cards.
The embedding method is generally used while manufacturing SIM cards. The first stage of this process consists in encapsulating an electronic component assembly comprising an integrated circuit and connecting wires into resin in order to protect the components of the electronic module. That encapsulated assembly is then glued into a cavity of a package, which may be made of plastic, for example. The package is often called the “card body”.
With the miniaturisation and the increase in the functions of mobile telephones, the format of SIM cards is ever smaller, and so is their thickness. The change from the 2FF form factor (25×15 mm2) to 3FF format (15×12 mm2) and soon to 4FF format reduces the gluing surface and the size of the components that can be integrated into the module.
Further, the reduction in the thickness of SIM cards is being studied, in order to reduce the volume of SIM cards in their readers and also to allow the insertion of small SIM cards into adapters that enable compatibility with the connectors of readers using older formats.
One drawback of the standard embedding method is that it does not make it possible to easily reduce the thickness of SIM cards below the current thickness of 0.80 mm. In that method, the resin that encapsulates the electronic component assembly can have surface irregularities and topology with height differences that are too large to be delivered to customers as a finished product. Besides, that surface relief does not comply with the thickness tolerances of mini cards or other integrated circuit packages.
To remedy that problem of surface irregularities, the standard method consists in inserting the encapsulated electronics component assembly—called the module—into a card body. However, that solution increases the thickness of the smart card. That is because it results in a stack including the hot melt adhesive that glues the electronic module to the card body, the gap between the module and the bottom of the card cavity and the thickness of the bottom of the card cavity. That stack represents at least 0.15 mm, thus limiting the possibility of reducing the thickness.
An additional drawback is that the card body manufactured according to the applicable ISO standard has an extended format in relation to the final format of the SIM card, regardless of that final format. As a result, the useful surface of the smart card, that is to say the surface available for the electronics components, limited. The card body is scored around the SIM card, and the user separates the two before using the SIM card. That is why embedding makes it necessary to use a large quantity of plastic, which increases the cost of the method.
The document WO 2010/094782 A1 discloses a method for manufacturing smart cards without resorting to embedding. The electronic module is covered with a coat of resin with dimensions that are slightly larger than those of the final format of the smart card. That coat of resin makes up the smart card package in itself.
One drawback is that the resin is dispensed using the Resin Transfer Moulding (or RTM) method, which requires costly investment in specialised equipment.
The document EP 0644507 B1 discloses a method for manufacturing smart cards without resorting to embedding. In that method, the electronic module comprises a cover platelet coated with resin on one side. The coated platelet is placed on the electronic module so that the resin covers the electronic module. The method makes it possible to reduce the final thickness of the module to 0.62 mm but it is still necessary to embed the module and thus have an additional thickness of plastic that is added to the thickness of the module.
Another drawback is that it requires specific equipment, which leads to an increase in costs.